Experimental determination of the effect of the ratio of B/Al on glass dissolution along the nepheline (NaAlSiO4)–malinkoite (NaBSiO4) join
Experimental determination of the effect of the ratio of B/Al on glass dissolution along the nepheline (NaAlSiO4)–malinkoite (NaBSiO4) join
复制标题
实验测定 B/Al 比对霞石 (NaAlSiO4)-菱铁矿 (NaBSiO4) 连接处玻璃溶解的影响
DOI：
10.1016/j.gca.2009.09.006
复制
发表时间：
2010
影响因子：
5
通讯作者：
J. Broady
中科院分区：
文献类型：
--
作者：
E. Pierce;L. R. Reed;W. Shaw;B. McGrail;J. Icenhower;C. Windisch;E. Cordova;J. Broady
采用溶解动力学方法研究了沿着NaAlSiO 4-NaBSiO 4界面的五种玻璃的溶解动力学，并分析了硼铝取代引起的结构变化对溶解速率的影响。每种玻璃的组成以Al 2 O3（5- 25摩尔%）和B 2 O3（20- 0摩尔%）的摩尔%相反地变化，Na 2 O（25摩尔%）和SiO 2（50摩尔%）构成剩余量，在每种情况下Na/（Al+B）=1.0。在稀释条件下作为溶液pH（7.0至12.0）和温度（23至90°C）的函数进行单程流通实验（SPFT）。通过27 Al和29 Si MAS-NMR分析未反应的玻璃样品表明Al（~ 98%[4]Al）和Si原子（~ 100%[4]Si）占据四面体配位，而B原子占据四面体（[4]B）和三角（[3]B）配位。[3]B的分布在[3]B（环）和[3]B（非环）部分之间分馏，[3]B（环）/[3]B（非环）比随着B/Al比的增加而增加。MAS-NMR结果还表明随着B/Al比的增加，[4]B的分数增加。随着B/Al比的增加，27 Al峰最大值移向较小的值，这表明[4]Al和[3]B位点之间发生混合，假设四面体三价阳离子之间相互回避（[4]Al-O-[4]B回避）。与27 Al和11 B光谱不同，29 Si光谱显示出一个更负的化学位移（化学位移范围在−88和− 84 ppm之间），并且随着B/Al比的增加，光谱宽度增加。未反应的玻璃样品的拉曼光谱也用于交叉检查从MAS-NMR收集的结果，并表明NeB 4（具有最高B含量的玻璃样品）可能由B-Na富集和Al-Si富集的微畴组成，这影响了测量的溶解速率。SPFT实验的结果表明，对于所有均匀玻璃，在中性至碱性测试条件下，反应的正向速率和pH幂律系数η与B/Al无关。温度依赖性显示，随着温度增加67°C，溶解速率增加一个数量级，并表明溶解受表面介导反应控制，如活化能Ea所示，Ea在44±8和48± 7 kJ/mol之间。基于Na和Si释放的均匀玻璃的正向溶解速率与B/Al比无关，而基于Al和B释放的溶解速率则不然。基于B释放的标准化溶出速率随[3]B（环）的摩尔分数而增加。最后，在雅阁与以前的研究，本文讨论的数据表明，无论是铝-O或硅-O键的断裂作为限速步骤控制这些玻璃的溶解。
The dissolution kinetics of five glasses along the NaAlSiO4–NaBSiO4join were used to evaluate how the structural variations associated with boron–aluminum substitution affect the rate of dissolution. The composition of each glass varied inversely in mol% of Al2O3(5–25mol%) and B2O3(20–0mol%) with Na2O (25mol%) and SiO2(50mol%) making up the remaining amount, in every case Na/(Al+B)=1.0. Single-pass flow-through experiments (SPFT) were conducted under dilute conditions as a function of solution pH (from 7.0 to 12.0) and temperature (from 23 to 90°C). Analysis of unreacted glass samples by27Al and29Si MAS-NMR suggests Al (∼98%[4]Al) and Si-atoms (∼100%[4]Si) occupy a tetrahedral coordination whereas, B-atoms occupy both tetrahedral ([4]B) and trigonal ([3]B) coordination. The distribution of[3]B fractionated between[3]B(ring) and[3]B(non-ring) moieties, with the[3]B(ring)/[3]B(non-ring) ratio increases with an increase in the B/Al ratio. The MAS-NMR results also indicated an increase in the fraction of[4]B with an increase in the B/Al ratio. The27Al peak maxima shift to lesser values with an increase in the B/Al ratio which suggests mixing between the[4]Al and[3]B sites, assuming avoidance between tetrahedral trivalent cations ([4]Al–O–[4]B avoidance). Unlike the27Al and11B spectra, the29Si spectra illustrate a subtle shift to more negative chemical shift (chemical shift range between −88 and −84ppm) and increases in the spectral widths as the B/Al ratio increases. Raman spectroscopy of unreacted glass samples was also used to cross-check the results collected from MAS-NMR and suggested that NeB4 (the glass sample with the highest B content) may consist of B–Na enriched and Al–Si enriched micro-domains, which affected the measured dissolution rates. Results from SPFT experiments suggest a forward rate of reaction and pH power-law coefficients, η, that are independent of B/Al under these neutral to alkaline test conditions for all homogeneous glasses. The temperature dependence shows an order of magnitude increase in the dissolution rate with a 67°C increase in temperature and suggests dissolution is controlled by a surface-mediated reaction, as indicated by the activation energy, Ea, being between 44±8 and 48±7kJ/mol. Forward dissolution rates, based on Na and Si release, for homogeneous glasses are independent of the B/Al ratio, whereas dissolution rates based on Al and B release are not. Normalized dissolution rates, based on B release, increase with the molar fraction of[3]B(ring). Finally in accord with previous studies, the data discussed in this manuscript suggest rupture of either the Al–O or Si–O bonds as the rate-limiting step controlling the dissolution of these glasses.